Abstract Because diagnostic criteria of concussion rely upon self-reporting?which may be unreliable in a recently concussed individual?the goal of this project is to identify a neural marker of concussion that does not require effort from the patient. Concussion adversely affects many domains and there is strong reason to believe, and preliminary data to support, that neural processing in the auditory system is negatively influenced by sports- related concussion. By using an objective electrophysiological measure of auditory processing, this work has strong potential to broaden the understanding of concussion's effect on sensory processing and to eliminate a major pitfall in diagnosis and management of concussion. This proposal uses a novel approach to understand the impact of head injury on sensory processing: the frequency-following response (FFR) to speech. The central hypothesis is this objective neurophysiological measure of auditory processing serves as a marker of disruptions to central nervous system function following concussion. In collaboration with Northwestern University Athletics, this is a prospective, longitudinal study of concussion and prolonged participation in contact/collision sports that follows ~500 student-athletes annually (~875 total) within and across sports seasons. In a typical year up to 15% of student-athletes are diagnosed with a concussion by a sports medicine physician. This provides a potent opportunity to investigate the impact of concussion on auditory processing in both the short-term (immediately after injury) and long-term (after a one- to four-year college athletic career). In the large group of non-concussed athletes, this project will establish whether, as hypothesized, auditory processing is more compromised over time in individuals participating in contact/collision sports. This project can elucidate the physiological mechanisms by which concussions and long-term participation in contact sports disrupt the central nervous system. The FFR will provide fine-grained insight into the nature of the physiological imprint of concussion. The longitudinal design in a large cohort provides powerful within- and between-subject controls for tracking head injuries and risk of injury based on sport in the short- and long-term stages, and opportunities for within-study replications. If successful, the FFR could one day serve as a fast, objective, and scalable clinical adjunct to assist in concussion diagnosis and management by indicating an individual's auditory processing profile following one or more concussions.